Electric charge controlling resin, toner made with the use of the same and method of producing the toner

ABSTRACT

The present invention provides electric charge controlling resin formed with the use of a polymer which has a polar group for imparting an electrostatic charge and of which flow rate Rf as measured by a thin-layer chromatography using silica gel as an adsorbent and ethyl acetate as a developing solvent, is in a range from 0.5 to 1.0. Toner may be prepared by mixing and dispersing the electric charge controlling resin in a binding resin, or by suspension-polymerizing a polymerizable composition under the condition where the electric charge controlling resin is contained in the composition to obtain a binding resin. The toner thus prepared is excellent in the electrostatic chargeability, humidity resistance, coloring properties and reproducibility.

FIELD OF THE INVENTION

The present invention relates to (i) electric charge controlling resinfor adjusting the electrostatic chargeability of toner used fordeveloping an electrostatic latent image, (ii) toner made with the resinand (iii) a method of producing the toner.

BACKGROUND OF THE INVENTION

In the field of electrophotographic copying or electrostatic printing,it is a common practice to use, for developing an electrostatic latentimage, toner in the form of colored resin particles containing coloringagents and electric charge controlling agents dispersed in a resinmedium.

Generally, the toner is composed of resin particles containing coloringagents, electric charge controlling agents and the like as mixed anddispersed in binding resin. To provide the toner with desired color andelectrostatic chargeability, it is a common practice to suitably changethe types and blending amounts of the binding resin, coloring agents,electric charge controlling agents and the like to be used.

As a toner manufacturing method, there is generally adopted a so-calledpulverization method by which a resin medium and coloring agents aremolten and kneaded to prepare toner in the form of particles having apredetermined range of particle size. However, the toner thus producedby the pulverization method contains particles having irregular shapesand presents a poor fluidity. Further, the individual irregularparticles of the toner are electrically, charged in considerablydifferent manners, causing the distribution of electrostatic charge tobecome broad. Further, the pulverization method requires facilities ofgreat size, resulting in increased production cost.

It is also proposed to manufacture toner by a suspension polymerizationmethod. According to this method, a polymeric composition in the form ofa mixture of an initiator of polymerization with toner characteristicimparting agents such as polymeric monomers, coloring agents, electriccharge controlling agents and the like, is suspended, under stirring ata high speed, in an aqueous solution containing a dispersion stabilizer.Then, this mixture is polymerized to directly produce toner. This tonermanufacturing method using suspension polymerization may directlyproduce toner in the form of particles of which sizes are in a practicalrange, at the resin polymerization step. This results in decrease inproduction cost. Further, this method presents the advantage that theresultant toner is excellent in fluidity and stability of electrostaticcharge.

Such a toner manufacturing method using pulverization or suspensionpolymerization uses an electric charge controlling agent for adjustingthe characteristics of toner electrostatic charge. As the electriccharge controlling agent, a variety of dyes are generally used. Sincethe electric charge controlling agent controls the developing propertiesof the toner, it is important to properly select the electric chargecontrolling agent.

More specifically, the demands for an image forming apparatus arerecently versatile according to applications and are extended to avariety of performances such as smaller-size, lower-energy,higher-speed, multi-colors, maintenance-free and the like. Accordingly,to accomodate to the developing system or inside environmentalconditions of the apparatus, the toner is required to have differentcharacteristics according to the apparatus types and colors used.Therefore, a great number of types of toner are apt to be produced in asmall amount. It is therefore required to manufacture, with goodreproducibility, toners of which characteristics are subtly different.In view of the foregoing, the selection of the electric chargecontrolling agent is important.

However, the dyes are hardly compatible with resin and a polymericmonomer. Accordingly, a great amount of dyes should be added to obtain asufficient electrostatic charge. Further, since the dyes are present inthe form of particles in resin and a polymeric monomer, theelectrostatic chargeability of the resultant toner considerably varywith the quality of dispersion of the dyes. Such variations may causeimage fog, toner scattering and uneveness of an image quality. Further,when the dyes are used for color toner requiring light permeability, thedyes dispersed in the form of particles inhibits such lightpermeability, failing to form a clear color image. In addition, the dyesare generally expensive, leading to increase in production cost.

In view of the foregoing, to uniformly stabilize the characteristics oftoner electrostatic charge, in particular to improve the startingelectrostatic chargeability, it is proposed to mix and uniformlydisperse binding resin and a copolymer, serving as electric chargecontrolling resin, composed of (i) a monomer having a polar group and(ii) an oil-soluble monomer compatible with the binding resin or amonomer capable of forming the binding resin, so that the electrostaticcharges of individual toner particles are made uniform. For example,Japanese Unexamined Patent Publication No. 88564/1988 discloses tonercontaining a polymer (copolymer) having a sulfonate group connected toan aromatic ring.

It is found that the sulfonate group disclosed in this Publication isexcellent in electric charge imparting properties and that the usethereof for toner improves the electrostatic chargeability such asstarting and stabilization of the electrostatic charge, and the like.

However, the inventors of the present invention have found the followingfacts. That is, even though the monomer having a polar group (sulfonategroup or the like) and the oil-soluble monomer in the electric chargecontrolling resin are substantially the same in monomer compositionratio, the dispersibility of the electric charge controlling resin inthe binding resin considerably depends on the polymer structure ormolecular weight of the electric charge controlling resin which varieswith change in production conditions, difference in raw materials usedbetween lots, and the like. This presents the problems that theelectrostatic chargeability undergo a change, that the water vaporresisting properties are lowered, and that the hue varies, failing torepeatedly produce the toner having desired characteristics with goodreproducibility.

Consideration is then made on the use of the electric charge controllingresin for manufacturing toner by the suspension polymerization method.The polar group for controlling the electric charge of the electriccharge controlling resin is also water-soluble. Accordingly, when theelectric charge controlling resin as mixed in a polymeric composition issubjected to suspension polymerization, the electric charge controllingresin is eluted from the suspension oil drops into water. Further, theemulsification by the water-soluble polar group of the electric chargecontrolling resin thus eluted, causes a by-product in the form ofparticles with 1 μm or less to be produced. This may not only reduce theproductivity, but also deteriorate the electrostatic chargeability,durability and water vapor resistance of the toner.

It is a main object of the present invention to provide electric chargecontrolling resin excellent in electric charge imparting properties anddispersion in binding resin.

It is another object of the present invention to provide electric chargecontrolling resin which is adapted not to be eluted in an aqueous phasein a suspension polymerization step while being maintained in suspensionoil drops until the polymerization is complete, and which may beuniformly and evenly dispersed in the oil drops.

It is a further object of the present invention to provide a tonerproducing method capable of manufacturing toner having improveddurability with good productivity and without production of a by-productin the form of particules at a suspension polymerization step.

It is still another object of the present invention to provide electriccharge controlling resin capable of imparting uniform and highlyreproducible electrostatic chargeability.

It is a still further object of the present invention to provide tonerhaving desired characteristics and a method of producing such toner in asystem of producing a great number of types of toner in a small amount.

It is yet another object of the present invention to provide toner whichmay be economically produced with increased productivity, and a methodof economically producing such toner with increased productivity.

It is a yet further object of the present invention to provide tonerwhich is excellent in starting and stability of electrostatic charge andlight permeability, and which is also excellent in coloring propertiesand water vapor resistance, and to provide a method of producing suchtoner.

DISCLOSURE OF THE INVENTION

The present invention provides electric charge controlling resin formedwith the use of a polymer which has a polar group for imparting anelectrostatic charge and of which flow rate Rf is in a range from 0.5 to1.0, this flow rate Rf being measured by a thin-layer chromatographyusing silica gel as an adsorbent and ethyl acetate as a developingsolvent.

In the electric charge controlling resin of the present invention, theflow rate Rf as measured by a thin-layer chromatography is in the rangeabove-mentioned, so that the hydrophilic and lipohilic property of thepolymer itself are in a preferred state. According to the presentinvention, such flow rate Rf serves as an index of lipohilic property.

In actual production of the electric charge controlling resin, a polymeras obtained through a polymerization reaction is used as a raw materialof toner after it has been made sure that the polymer presents the flowrate Rf in the range above-mentioned. Dissolving the obtained polymer ina water-soluble organic solvent, and loading the resultant solution intowater to remove the components of the polymer apt to be dissolved inwater, the flow rate Rf is more suitable.

First toner in accordance with the present invention may be prepared bymixing and dispersing such electric charge controlling resin in bindingresin. If the flow rate Rf of the polymer forming the electric chargecontrolling resin is less than 0.5, the hydrophilic property of thepolymer is so strong that the dispersion of the electric chargecontrolling resin in the binding resin becomes uneven. This producestoner particles of which electrostatic charges are excessively great orless. The variations of the toner characteristics due to dispersion iswide, so it becomes difficult to adjust the toner characteristics to thedesired characteristics by adjusting the blending ratio, failing tomanufacture desired toner with good reproducibility.

According to the first toner, the dispersed and mixed electric chargecontrolling resin has hydrophilic and lipohilic property in a preferredstate. Thus, the toner is excellent in the electrostatic chargeability,water vapor resistance, coloring properties and reproducibility. It istherefore possible to produce, with high reliability, toners having avariety of performances suitable for various systems, by suitablydetermining amounts of components such as electric charge controllingresin and the like to be added to the binding resin.

Second toner of the present invention may be manufactured by suspensionpolymerization using the electric charge controlling resin. That is,binding resin as containing the electric charge controlling resin issubjected to suspension polymerization.

The suspension polymerization may be carried out with the electriccharge controlling resin mixed added to a polymeric composition whichcontains polymeric monomers and coloring agents.

More specifically, the electric charge controlling properties of theelectric charge controlling resin are determined, to a certain extent,by the number of polar groups in the polymer (in a copolymer, by thecomposition ratio of the monomer having a polar group to the oil-solublemonomer). However, the dispersion quality of the electric chargecontrolling resin at the time of suspension polymerization, i.e., therelationship between the solubility of the electric charge controllingresin in a water phase and the compatibility thereof with the polymericmonomer, varies with the structure, molecular weight and polymerizationconditions of the copolymer, difference in raw materials used betweenlots and the like. Accordingly, the preferred conditions of the electriccharge controlling resin used for suspension polymerization have notbeen conventionally grasped well. According to the present invention,the use of the particular electric charge controlling resin mentionedabove, not only improves the compatibility with the polymeric monomersforming oil drop particles, but also prevents the resin from beingdissolved in a water phase. Thus, the electric charge controlling resinis uniformly dispersed in oil drop particles. Further, thepolymerization may proceed with the electric charge controlling resinexisting on the surfaces of the oil drops without the electric chargecontrolling resin eluted in a water phase. It is therefore possible toprepare spheric toner particles of which difference in characteristicsis small and which are excellent in the electrostatic chargeability,durability and water vapor resistance. The following description willdiscuss in detail the present invention.

Electric Charge Controlling Resin

In the electric charge controlling resin of the present invention,examples of the polar group for imparting an electrostatic chargeinclude a sulfonate group, a carboxylate group, an amine salt group andthe like. Preferably, there is used a sulfonate group represented by--SO₃ X (wherein X is a sodium element, a potassium element or a calciumelement).

The polymer forming the electric charge controlling resin may be amonopolymer. Preferably, this polymer is a copolymer as obtained by apolymerization reaction such as bulk polymerization, suspensionpolymerization, solution polymerization, emulsion polymerization,dispersion polymerization or the like, of a monomer having a polar group(a sulfonate group) and an oil-soluble monomer.

Examples of the monomer having the sulfonate group include salts such assodium, potassium, calcium and the like of styrene sulfonic acid, vinylsulfonic acid, methyl propane sulfonic acid, methacrylsulfonic acid orthe like. Of these, styrene-sodium sulfonic acid produces preferredresults.

As the oil-soluble monomer, there may be suitably selected a monomerexcellent in compatibility with the binding resin for producing thefirst toner, or a monomer excellent in compatibility with monomercomponents forming the binding resin for producing the second toner bysuspension polymerization. Generally, the same oil-soluble monomer maybe used as the oil-soluble monomer used for the first toner and as theoil-soluble monomer used for the second toner.

Examples of the oil-soluble monomer include vinyl aromatic hydrocarbon,an acrylic monomer, a vinyl ester monomer, a vinyl ether monomer, adiolefin monomer, a monoolefin monomer and the like.

The vinyl aromatic hydrocarbon may be represented by the followingformula (1): ##STR1## (wherein R₁ is a hydrogen atom, a lower alkylgroup or a halogen atom, and R₂ is a hydrogen atom, a lower alkyl group,a halogen atom, an alkoxy group, a nitro group or a vinyl group).

Examples of the vinyl aromatic hydrocarbon above-mentioned includestyrene, α-methylstyrene, vinyl toluene, α-chlorostyrene, o-, m-,p-chlorostyrene, p-ethylstyrene, divinyl benzene and the like. Thesesubstances may be used either alone or in combination of plural types.

The acrylic monomer may be represented by the following formula (2):##STR2## (wherein R₃ is a hydrogen atom or a lower alkyl group, and R₄is a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms, ahydroxy alkyl group, or a vinyl ester group).

Examples of the acrylic monomer above-mentioned include methyl acrylate,ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexylacrylate, phenyl acrylate, methyl methacrylate, hexyl methacrylate,2-ethylhexyl methacrylate, β-hydroxy ethyl acrylate, γ-hydroxy propylacrylate, α-hydroxy butyl acrylate, β-hydroxy ethyl methacrylate,ethylene glycol ethyl methacrylate, tetra methylene glycol esterdimethacrylate and the like.

The vinyl ester monomer includes vinyl esters represented by thefollowing formula (3): ##STR3## (wherein R₅ is a hydrogen atom or alower alkyl group).

Examples thereof include vinyl formate, vinyl acetate, vinyl propionateand the like.

The vinyl ether monomer is vinyl ether represented by the followingformula (4): ##STR4## (wherein R₆ is a mono hydrocarbon group having 1to 12 carbon atoms).

Examples of the vinyl ether above-mentioned include vinyl-n-butyl ether,vinyl phenyl ether, vinyl cyclohexyl ether and the like.

The diolefin monomer is diolefins represented by the following formula(5): ##STR5## (wherein R₇, R₈ and R₉ may be the same or different, andeach is a hydrogen atom, a lower alkyl group or a halogen atom).Examples of the diolefins above-mentioned include butadiene, isoprene,chloroprene and the like.

The monoolefin monomer is monoolefins represented by the followingformula (6): ##STR6## (wherein R₁₀ and R₁₁ may be the same or different,and each is a hydrogen atom or a lower alkyl group.) Examples of themonoolefins above-mentioned include ethylene, propylene, isobutylene,butene-1, pentane-1, 4-methyl pentane-1 and the like.

Of these, the styrene monomer and the acrylic monomer are preferred.

The blending ratio of the oil-soluble monomer to the monomer having apolar group such as the sulfonate group or the like depends on themonomers used, but may be generally selected in a range from 30:70 to1:99, and preferably from 20:80 to 2:98. Then, the monomers aresubjected to a polymerization reaction such as bulk polymerization,suspension polymerization, solution polymerization, emulsionpolymerization, dispersion polymerization or the like, thereby toproduce a copolymer. The molecular weight of the copolymer may beadjusted such that the average molecular weight is in a range from 10³to 10⁶. The average molecular weight is preferably in a range from about10⁴ to about 10⁶ for making the first toner, and in a range from about103 to about 50000 for making the second toner.

Preferably, the structure of the copolymer is a random copolymer or analternating copolymer.

Preferably, the production of the electric charge controlling resin ismade by the dispersion polymerization out of the polymerization methodsabove-mentioned for the following reasons.

That is, most of polymers and monomers having a polar group present alow compatibility with the monomer for forming a polymer having a highcompatibility with binding resin. Accordingly, when the bulkpolymerization or the suspension polymerization is applied, the monomersare apt to become uneven before or during the polymerization.Accordingly, there may be easily produced a copolymer containing a greatnumber of monomer units having a polar group and having no compatibilitywith the binding resin.

The solution polymerization presents the similar problem as in the bulkpolymerization. However, when a suitable solvent is selected, a uniformsystem may be obtained before the polymerization. However, even in thesolution polymerization, when the polymerization proceeds, the polymeris apt to be separated out and the composition of the polymer thusseparated out is apt to be uneven. To control the separating of thepolymer in the solution polymerization, it is required to minimize thehold-up or to lower the ratio of the polar monomers.

According to the emulsion polymerization, it is relatively easy tocontrol the composition of the monomer units of a copolymer to beproduced. However, the molecular weight is increased to lower thecompatibility with the binding resin.

In the dispersion polymerization, a mixture medium of water and awater-miscible organic solvent is used as a polymerization medium. Inthis polymerization, the water naturally dissolves a water-solublemonomer, and the water-miscible organic solvent dissolves theoil-soluble medium. Both-type monomers are dissolved in the mixturemedium, thereby to form a homogenized solution phase.

At the initial stage of polymerization, the reaction proceeds in theform of a solution polymerization to produce a copolymer of whichmolecular weight is low and which has the composition of monomer unitsaccording to the reactivity ratio. When the reaction further proceeds,the copolymer is apt to be separated out. However, since a dispersionstabilizer is present, some particles of the copolymer become relativelystable dispersible particles. These dispersible particles are acopolymer of the oil-soluble monomer and the water-soluble monomer.Accordingly, the water-soluble monomer and the oil-soluble monomer whichhave not yet been reacted in a continuous phase, are simultaneouslyabsorbed, thereby to produce a copolymer having a relatively evencomposition.

Examples of the water-miscible organic solvent used for the dispersionpolymerization include: lower alcohols such as methanol, ethanol,isopropanol or the like; ketones such as acetone, methyl ethyl ketone,methyl butyl ketone or the like; ethers such as tetrahydrofuran, dioxaneor the like; esters such as ethyl acetate or the like; and amides suchas dimethylformamide or the like. These substances may be suitablyselected and used according to the types of the monomers used.

The blending ratio by weight of the water to the water-miscible organicsolvent depends on the types of the solvent and the monomers used, butis generally in a range from 40:60 to 5:95, and preferably in a rangefrom 30:70 to 10:90. This ratio may be so selected as to form a uniformsolution phase in its entirety. The blending ratio by weight of themixture medium to the monomers is in a range from 0.5 to 50 times permonomer, and preferably in a range from 5 to 25 times.

The dispersion stabilizer is a polymeric dispersion stabilizer solublein the mixture medium mentioned above. Preferred examples of thedispersion stabilizer include polyacrylic acid, polyacrylate,polymethacrylic acid, polymethacrylate, a (metha)acrylicacid-(metha)acrylic ester copolymer, an acrylic acidvinyl ethercopolymer, a methacrylic acid-styrene copolymer, carboxymethylcellulose,polyethylene oxide, polyacrylamide, methylcellulose, ethylcellulose,hydroxyethylcellulose, polyvinyl alcohol and the like. A nonionic oranionic surface active agent may also be used. In the system, thedispersion stabilizer may be used at a ratio of 0.01 to 10% by weight,and preferably 0.1 to 3% by weight.

As the initiator of polymerization, there may be used an initiatorsoluble in a water-insoluble monomer, including (i) an azo compound suchas azobisisobutyronitrile and the like and (ii) peroxide such as cumenehydroperoxide, t-butylhydroperoxide, dicumyl peroxide,di-t-butylperoxide, benzoyl peroxide, lauroyl peroxide and the like. Inaddition, there may be used a combination of ultraviolet rays or ionizedradiation such as γ-rays, accelerating electron beams with any of avariety of light sensitizer.

The blending amount of the initiator of polymerization such as the azocompound, peroxide or the like may be a so-called proper catalyticamount, and is generally in a range from 0.1 to 10% by weight per chargemonomer. As the polymerization temperature and time, there may beapplied conventional temperature which is generally in a range from 40°to 100° C., and conventional time which is generally in a range from 1to 50 hours. The reaction system may be stirred in a moderate mannersuch that the generally homogenized reaction is achieved. To prevent thepolymerization from being restrained by oxygen, the reaction system maybe polymerized with the atmosphere replaced with an inert gas such asnitrogen.

According to this polymerization, the electric charge controlling resinmay be obtained in the form of particles generally having a relativelyuniform distribution of particle size from 0.01 to 10 μm, and preferablyfrom 0.1 to 7 μm.

Further preferred results may be produced in the following manner. Thatis, the resultant polymerization product may be dissolved in a suitablewater-soluble organic solvent such as tetrahydrofuran, dioxane, dimethylsulfoxide, acetone or the like. The resultant solution may be loaded inwater, so that the polymeric components apt to be dissolved in water areremoved. After filtered off or centrifugalized, the residue may be driedto produce the electric charge controlling resin. The flow rate Rf ofthe electric charge controlling resin thus produced is measured by thethin-layer chromatography mentioned above. It is then checked whether ornot the spot position appears in a range from 0.5 to 1.0. Based on theresult, the characteristics of the electric charge controlling resin areevaluated. Preferred is the electric charge controlling resin in whichthe spot position appears in a range from 0.7 to 1.0.

Production of the First Toner

Together with additives such as coloring agents and the like, theelectric charge controlling resin thus obtained is contained in bindingresin.

Examples of the binding resin include: an olefin polymer such as astyrene polymer, an acrylic polymer, a styrene-acryl copolymer,chlorinated polyethylene, polypropylene, ionomer or the like; and avariety of polymers such as polyvinyl chloride, polyester, polyamide,polyurethane, epoxy resin, diallylphthalate resin, phenol resin, rosinmodified maleic acid resin, rosin ester, petroleum resin and the like.Preferably, the binding resin is mainly composed of a styrene polymer,an acrylic polymer or a styrene-acrylic polymer. The polymer has anaverage molecular weight in a range from 30000 to 250000, and preferablyfrom 50000 to 200000. The polymers above-mentioned may be used eitheralone or in combination of plural types.

Among the polymers, rosin ester, rosin modified phenol resin, rosinmodified maleic acid resin, epoxy resin, polyester, a fibrous polymer,polyeter resin and the like are advantageous for improving thefrictional electrostatic charge characteristics of toner.

In view of the fixing properties and durability, there may be used thepolymers having a softening point in a range from 50° to 200° C., andpreferably from 70° to 170° C.

Examples of the coloring agents include the following pigments and dyes.

Black Pigment

Carbon black, Acetylene black, Lamp black, Aniline black

Yellow Pigment

Chrome yellow, Zinc yellow, Cadmium yellow, Yellow oxide of iron,Mineral fast yellow, Nickel titanium yellow, Navel's yellow, Tephtholyellow S, Hansa yellow 10G, Benzidine yellow-G, Quinoline yellow lake,Permanent yellow NGG, Tartrazine lake.

Orange Pigment Chrome orange, Molybdenum orange, Permanent orange GTR,Pyrazolone orange, Vulcan orange, Indanthrene brilliant orange RK,Benzidine orange G, Indanthrene brilliant orange GK

Red Pigment

Red iron oxide, Cadmium red, Red lead, Cadmium mercury, Permanent Orange4R, Lithol red, Pyrazolone red, Watching red calcium salt, Lake red D,Brilliant carmine 6B, Eosine lake, Rhodamine lake B, Alizarine lake,Brilliant carmine 3B

Violet Pigment

Manganese violet, Fast violet B, Methyl violet lake

Blue Pigment

Prussian blue, Cobalt blue, Alkali blue lake, Victoria blue lake,Phthalocyanine blue, Metal-free phthalocyanine blue, Partiallychlorinated phthalocyanine blue,

Fast sky blue, Indanthrene blue BC

Green Pigment

Chrome green, Chrome oxide, Pigment green B, Malachite green lake, Fanalyellow green G

White Pigment

Zinc white, Titanium oxide, White of antimony, Zinc sulfide

Extender Pigment

Pearlite powder, Barium carbonate, Clay, Silica, White carbon, Talc,Aluminum white

As magnetic material pigments, there are known triiron tetroxide (Fe₃O₄), iron sesquioxide (γ-Fe₂ O₃), zinc iron oxide (ZnFe₂ O₄), yttriumiron oxide (Y₃ Fe₅ O₁₂), cadmium oxide (Cd₃ Fe₅ O₁₂), copper iron oxide(CuFe₂ O₄), lead iron oxide (PbFe₁₂ O₁₉), neodymium iron oxide (NdFeO₃),barium iron oxide (BaFe₁₂ O₁₉), magnesium iron oxide (MgFe₂ O₄),manganese iron oxide (MnFe₂ O₄), lanthanum iron oxide (LaFeO₃), ironpowder (Fe), cobalt powder (Co), nickel powder (Ni) and the like.According to the present invention, any fine powder of these knownmagnetic materials may be used.

The blending ratio of the coloring agents to the binding resin may beconsiderably changed, but is generally in a range from 1 to 20 parts byweight per 100 parts by weight of the binding resin, and preferably from3 to 10 parts by weight per 100 parts by weight of the binding resin.

To impart toner fixing properties and off-set preventing properties,there may be used (i) any type of a variety of waxes includingpolypropylene having a low molecular weight, polyethylene having a lowmolecular weight, paraffin wax and the like, (ii) an olefin polymerhaving a low molecular weight containing an olefin monomer having 4 ormore carbon atoms, (iii) fatty acid amide, or (iv) silicone oil or thelike, at a ratio of 0.1 to 10 parts by weight and preferably 1 to 5parts by weight per 100 parts by weight of the binding resin.

There may be jointly used, as necessary, a conventional electric chargecontrolling agent such as metal-containing azo dyes, pyrimidinecompounds, metallic chelates of alkyl salicylic acid and the like, insuch an amount as not to produce any problem due to defectivedispersion.

There are molten and kneaded, together with additivies such as coloringagents and the like, the binding resin and the electric chargecontrolling resin having flow rate Rf of 0.5 to 1.0 as measured by thethin-layer chromatography mentioned above. After cooled, the resultantmixture is pulverized and classified, thereby to produce the firsttoner. Alternately, the first toner may be obtained by other method suchas a spray dry method.

The toner thus obtained may be subjected, as necessary, to surfacetreatment with fine particles of: carbon black; hydrophobic silica;metal oxide such as aluminum oxide and the like; fatty acid metallicsalt such as zinc stearate, zinc palmitate and the like; and resin suchas an acrylic polymer and the like, thereby to produce the final toner.

Production of the Second Toner (suspension polymerization)

As the polymeric monomer which may form the binding resin forming thepolymerizable composition, there may be used a polymerizable monomercompatible with the oil-soluble monomer forming the electric chargecontrolling resin. Examples of such a polymerizable monomer includevinyl aromatic hydrocarbon, an acrylic monomer, a vinyl ester monomer, avinyl ether monomer, a diolefin monomer, a monoolefin monomer and thelike, similar to the oil-soluble monomer above-mentioned.

There may be used coloring agents to be added to the polymerizablecomposition which are similar to those used for making the first toner.

In polymerization, the polymerizable composition composed of theelectric charge controlling resin, the polymerizable monomer forming thebinding resin, coloring agents and the like, is loaded in a water phaseand subjected to suspension and dispersion, thereby to form oil dropparticles. A dispersion stabilizer may be used to stabilize theparticles in the micron order without the oil drop particlesagglomerated.

A conventional dispersion stabilizer may be used. It is possible to use,as the dispersion stabilizer, a water-soluble polymer such as polyvinylalcohol, methylcellulose or the like, and a surface active agent of thenonionic type or the ionic type. However, fine powder ofwater-solution-retardant inorganic salt are preferred because they maystably maintain the oil drops in the form of fine particles without norestrictions imposed on the stirring speed, the blending amount and thelike. Examples of such salt include calcium phosphate, sodium phosphate,magnesium carbonate, barium carbonate, calcium carbonate, aluminumhydroxide and the like. Of these, the salt of phosphate is preferred inview of excellent stability of particles and easy removal from theproduced polymerizable particles. When water-solution-retardantinorganic salt is used, the joint use of a surface active agent mayincrease the stability.

The dispersion stabilizer may be used at a ratio of 1 to 50% by weightper water and preferably 10 to 25% by weight. The surface active agentis preferably used at a ratio of 0.01 to 0.1% by weight per water.

The suitable stirring speed applied at the time of suspension isgenerally in a range from 5000 to 15000 rpm.

The amount of the dispersion stabilizer and the stirring speed may besuitably adjusted such that the particle sizes of the suspension oildrops are in a range from 5 to 30 μm, and preferably from 8 to 12 μm.

As the initiator of polymerization, there may be used an oil-solubleinitiator of which examples include an azo compound such asazobisisobutyronitrile and the like, and peroxide such as cumenehydroperoxide, t-butylperoxide, dicumyl peroxide, di-t-butylperoxide,benzoyl peroxide, lauroyl peroxide and the like.

The blending amount of the initiator of polymerization such as the azocompound, the peroxide or the like is a so-called proper catalyst amountwhich is generally in a range from 0.1 to 10% by weight per chargemonomer. As the polymerization temperature and time, there may beapplied conventional temperature which is generally in a range from 40°to 100° C., and conventional time which is generally in a range from 1to 50 hours. The reaction system may be stirred in a moderate mannersuch that a homogenized reaction occurs in the entirety of the system.To prevent the polymerization from being restrained due to oxygen, thereaction system may be polymerized with the atmosphere replaced with aninert gas such as nitrogen or the like. According to the presentinvention, additive components preferred to be contained in the tonermay be previously blended in the polymerizable composition together withthe coloring agents and the electric charge controlling resin, prior tothe polymerization. For example, dyes may be added in order to stabilizethe atmosphere or to facilitate the starting of electrostatic charge.Further, to prevent the off-set, it is possible to add polyethylene oflow molecular weight, polypropylene of low molecular weight, a varietyof waxes, silicone oil or the like. Such additive components may beadded in such small amounts as to exert no influences upon thepolymerization and the characteristics of the particles to be produced.

After reaction, the polymerized product is obtained in the form ofspherical particles of which sizes are in the range mentioned above andon the surfaces of which the polar group for controlling the electriccharge is uniformly present. The produced particles are filtered off andwashed with water, acid, alkali or a suitable solvent, as necessary. Theparticles are then dried, thus producing toner particles.

The toner particles thus obtained may be covered, as necessary, withfine particles of metallic oxide such as carbon black, hydrophobicsilica, aluminum oxide or the like, or fine particles of resin such asan acrylic polymer or the like, thus producing the final toner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view illustrating developed spots of electric chargecontrolling resins used in Examples and Comparative Examples, asobtained by a thin-layer chromatography;

FIGS. 2 and 3 are graphs illustrating the electrostatic chargedistribution curves of the toners of Example 2 and Comparative Example1, respectively;

FIGS. 4 and 5 are graphs illustrating the electrostatic chargedistribution curves of the toners of Example 7 and Comparative Example3, respectively; and

FIG. 6 is a section view of apparatus for measuring the electrostaticcharge of toner.

Industrial Applicability

When producing the first toner with the use of the electric chargecontrolling resin of the present invention, the electric chargecontrolling resin excellent in dispersion in the binding resin may bepreviously selected prior to its mixing to the binding resin.Accordingly, it is possible not only to prevent the production ofdefective toner, but also to produce, with good reproducibility, tonerexcellent in the rising and stability of electrostatic charge and watervapor resistance. This results in improvements in production efficiency,thus achieving easy production of various toners suitable for a varietyof systems with low cost.

When producing the second toner with the use of the electric chargecontrolling resin of the present invention, there may be produced, withgood reproducibility and without production of by-product particles,durable spheric toner of which particle size distribution is sharp, ofwhich the starting of electrostatic charge is fast and of whichelectrostatic charge distribution curve is also sharp. Accordingly,there is no likelihood that defective toner is produced, resulting indecrease in production cost.

Examples

The following description will discuss the present invention in detailwith reference to Examples thereof and Comparative Examples.

Example 1 (production of electric charge controlling resin)

According to the prescriptions shown in Table 1, styrene, styrene-sodiumsulfonic acid, polyacrylic acid and azoisobutyronitrile were dissolvedin an alcohol-water mixed solvent. While being stirred under a stream ofnitrogen in a separable flask at 150 rpm, the mixtures were respectivelyreacted at temperatures shown in Table 2 for 12 hours, thus completingthe polymerization. The resultant emulsions were centrifugalized toseparate the particles therein, thus preparing powders ofstyrene-styrene sodium sulfonic acid copolymers DN-1 to DN-7. FIG. 1shows spots of the respective samples of the copolymers as developedaccording to a thin-layer chromatography with the use of silica gel asan adsorbent and ethyl acetate as a developing solvent. Table 2 alsoshows the average molecular weights and Rf values of DN-1 to DN-7.

                  TABLE 1 (1/2)                                                   ______________________________________                                                   (unit: % by weight)                                                           DN-1  DN-2      DN-3    DN-4                                       ______________________________________                                        Styrene      9.0     9.0       9.0   9.0                                      Styrene-sodium                                                                             1.0     1.0       1.0   1.0                                      sulfonic acid                                                                 Isopropyl alcohol              65.8  79.9                                     Methanol     66.6    66.6                                                     Water        22.2    22.2      22.2  8.9                                      Polyacrylic acid                                                                           1.0     1.0       1.0   1.0                                      Azobisiso-   1.0     1.0       1.0   0.2                                      butyronitrile                                                                 ______________________________________                                    

                  TABLE 1 (2/2)                                                   ______________________________________                                                   (unit: % by weight)                                                           DN-5      DN-6    DN-7                                             ______________________________________                                        Styrene      9.0         9.0     9.0                                          Styrene-sodium                                                                             1.0         1.0     1.0                                          sulfonic acid                                                                 Isopropyl alcohol                                                                          65.8        65.8                                                 Methanol                         66.6                                         Water        22.2        22.2    22.2                                         Polyacrylic acid                                                                           1.0         1.0     1.0                                          Azobisiso-   1.0         1.0     1.0                                          butyronitrile                                                                 ______________________________________                                    

                  TABLE 2 (1/2)                                                   ______________________________________                                                   DN-1   DN-2     DN-3     DN-4                                      ______________________________________                                        Gross weight 2500     4000     2500   2500                                    of polymerizable                                                              composition (g)                                                               Flask capacity                                                                               3        5        3      3                                     (liter)                                                                       Polymerization                                                                              60       60       80     70                                     temperature                                                                   (°C.)                                                                  Average molecular                                                                          8.7 × 10.sup.5                                                                   8.4 × 10.sup.5                                                                   2.6 × 10.sup.3                                                                 9.5 × 10.sup.4                    weight                                                                        Rf           0.84-0.99                                                                              0.86-0.97                                                                              0.92-0.99                                                                            0.42-0.99                               ______________________________________                                    

                  TABLE 2 (2/2)                                                   ______________________________________                                                    DN-5     DN-6     DN-7                                            ______________________________________                                        Gross weight  2500       4000     2500                                        of polymerizable                                                              composition (g)                                                               Flask capacity                                                                                3          5        3                                         (liter)                                                                       Polymerization                                                                              80          80       60                                         temperature                                                                   (°C.)                                                                  Average molecular                                                                           2.6 × 10.sup.3                                                                     8.4 × 10.sup.3                                                                   8.7 × 10.sup.5                        weight                                                                        Rf            0.94-0.99  0.92-0.97                                                                              0.86-0.99                                   ______________________________________                                    

Example 2 (production of the first toner)

    ______________________________________                                        (Component)            (Quantity)                                             ______________________________________                                        DN-1 (Rf value: 0.84-0.99)                                                                           10 parts by weight                                     Styrene-Acryl copolymer                                                                              80 parts by weight                                     (Tg = 65, Mn = 10000, Mw = 120000)                                            C.I. Solvent Blue 25   10 parts by weight                                     ______________________________________                                    

The components above-mentioned were dissolved, kneaded, pulverized andclassifed, thereby to produce toner having the average particle size of10 μm. The toner thus produced was mixed with a ferrite carrier toproduce a developer. This developer presented the toner electrostaticcharge of -36 μc/g as measured according to a blow-off method. Thedistribution of the toner electrostatic charge as measured withapparatus for measuring the electrostatic charge of toner, was sharp asshown in FIG. 2, which shows no toner particles presenting excessivelygreat or less electrostatic charges.

With the use of an OHP film, a copying test was conducted on thisdeveloper as mounted on the electrophotographic copying apparatusDC-1205 (manufactured by Mita Kogyo Co., Ltd.). The image obtained wasexcellent in light permeability with a good image quality.

Example 3 (production of the first toner)

Toner was prepared in the same manner as in Example 2 except that 10parts by weight of the DN-2 (Rf value : 0.86 to 0.97) was used insteadof the DN-1 used in Example 2. This toner presented the amount ofelectrostatic charge of -38 μc/g as measured according to the blow-offmethod. Likewise in Example 2, the distribution curve of electrostaticcharge was sharp and there were observed no toner particles presentingexcessively great or small electrostatic charges.

Likewise as in Example 2, a copying test was conducted on this toner.The image obtained was excellent in light permeability with a good imagequality.

Example 4 (production of the first toner)

Toner was prepared in the same manner as in Example 2 except that 10parts by weight of the DN-3 (Mw=2.6×10³) (Rf value : 0.92 to 0.99) wasused instead of the DN-1 (Mw=8.7×10⁵) used in Example 2, the DN-3 havinga molecular weight smaller than that of the DN-1. This toner presentedthe same performance as those of the toner of Example 2. However, thematerials remarkably sticked to the machine at the steps of preliminarymixing, fine pulverization and classification of the materials.

Likewise, as in Example 2, a copying test was conducted on this toner.The image obtained was excellent in light permeability with a good imagequality.

Comparative Example 1 (production of the first toner)

Toner was prepared in the same manner as in Example 2 except that 10parts by weight of the DN-4 (Rf value : 0.42 to 0.99) was used. Thistoner presented the electrostatic charge as low as -10 μc/g as measuredaccording to the blow-off method. According to the electrostatic chargedistribution of this toner, there were observed a great number of tonerparticles which were excessively or reversely charged, as shown in FIG.3.

Likewise as in Example 2, a copying test was conducted on this toner.The image obtained was poor in light permeability and lacked clearness.

Example 5 (production of the electric charge controlling resin)

    ______________________________________                                        (Component)         (Quantity)                                                ______________________________________                                        Styrene             4.3    parts by weight                                    Styrene-Sodium sulfonic acid                                                                      0.5    parts by weight                                    1,4-dioxane         88.3   parts by weight                                    Water               5.7    parts by weight                                    Azobisisobutyronitrile                                                                            1.2    parts by weight                                    ______________________________________                                    

The components above-mentioned were mixed. While being stirred under astream of nitrogen in a separable flask at 70 rpm, the mixture wasreacted at temperature of 70° C. for 12 hours. The mixture was loaded ina great amount of methanol. The polymer was deposited to remove theresidual monomers, and then centrifugalized to separate powder of theseparated copolymer. The powder thus separated was dried, thus producingelectric charge controlling resin SN-1. The SN-1 was then dispersed anddissolved in tetrahydrofuran (THF), and then loaded in a great amount ofwater. After deposited to the deepest depth, the SN-1 was sufficientlycleaned to remove the copolymerizable composition containing a greatamount of units of styrene-sodium sulfonic acid. The SN-1 thus cleanedwas again centrifugalized to take out an oil-soluble styrene-sodiumsulfonic acid copolymer. The copolymer thus taken out was dried, thusproducing electric charge controlling resin SN-2. Table 3 shows theconcentrations of styrene-sodium sulfonic acid and the Rf values of theSN-1 and SN-2 as calculated based on an infrared absorption spectrum.FIG. 1 shows spots of the acquired copolymers as developed according toa thin-layer chromatography.

                  TABLE 3                                                         ______________________________________                                                        SN-1  SN-2                                                    ______________________________________                                        Concentration of  10.4    5.2                                                 styrene-sodium                                                                sulfonic acid                                                                 (% by weight)                                                                 Rf                0 to 1.0                                                                              0.7 to 1.0                                          ______________________________________                                    

Example 6 (production of the first toner)

    ______________________________________                                        (Component)            (Quantity)                                             ______________________________________                                        SN-2 (Rf value: 0.7-1.0)                                                                             24 parts by weight                                     Styrene-Acryl copolymer                                                                              80 parts by weight                                     (Tg = 65, Mn = 10000, Mw = 120000)                                            C.I. Solvent Blue 25   10 parts by weight                                     ______________________________________                                    

According to the prescription above-mentioned, toner was prepared in thesame manner as in Example 2. This toner presented the electrostaticcharge of -40 μc/g as measured according to the blow-off method. Thedistribution curve of electrostatic charge was sharp with no tonerparticles presenting excessively great or small electrostatic charges.

Likewise, as in Example 2, a copying test was conducted on this toner.The image obtained was excellent in light permeability with a good imagequality.

Comparative Example 2 (production of the first toner)

Toner was prepared in the same manner as in Example 6 except that 24parts by weight of the SN-1 was used instead of the SN-2 used in Example6.

This toner presented the electrostatic charge of -12 μc/g as measuredaccording to the blow-off method. According to the distribution ofelectrostatic charge, there were observed many toner particlespresenting excessive or reverse electrostatic charges.

Likewise, as in Example 2, a copying test was conducted on this toner.The image obtained was poor in light permeability and lacked clearness.

As apparent from the Examples and Comparative Examples above-mentioned,the DN-1 and the DN-2 were prepared under the same polymerizationconditions except for the conditions of flask and charge amount, butpresent different Rf values serving as indexes of lipophilic property.The use of the DN-3 of which average molecular weight is lower than thatof the DN-1 or DN-2, caused the materials to stick to the machine at thetime of production. Nevertheless, the DN-3 may also produce tonerexcellent in the electrostatic chargeability and light permeability,likewise in Examples 2 and 3.

According to Example 6, the toner was prepared with the use of the SN-2(presenting the Rf value in a range from 0.7 to 1.0) which had beenobtained by dispersing and dissolving the SN-1 in the THF and by loadingthe SN-1 in water to remove the unnecessary copolymerizable composition.The toner of Example 6 may produce very good results. On the other hand,no toner was obtained with the use of the SN-1 of Comparative Example 2(presenting the Rf value of 0.1 to 1.0) which remained containing theunnecessary copolymerizable composition.

It was understood that any toner as obtained with the use of theelectric charge controlling resin presenting the Rf value in a preferredrange, was good and that the production control using a thin-layerchromathography at the time of production of the electric chargecontrolling resin was very effective in checking the quality of tonerproduced on a full scale.

Example 7 (production of the second toner)

    ______________________________________                                        (Component)            (Quantity)                                             ______________________________________                                        DN-5 (Rf value: 0.94-0.99)                                                                           10    parts by weight                                  Styrene                60    parts by weight                                  Graphitized carbon black                                                                             5     parts by weight                                  (MA-100 manufactured by                                                       Mitsubishi Kasei Co., Ltd.)                                                   Polypropylene of low molecular                                                                       1.5   parts by weight                                  weight (BISCOL 550P manufactured                                              by Sanyo Kasei Co., Ltd.)                                                     Initiator of polymerization                                                                          4     parts by weight                                  (AIBN)                                                                        ______________________________________                                    

The components above-mentioned were mixed to produce a polymerizablecomposition.

Hydrochloric acid was added to a dispersion medium as obtained bymixingly adding 5.5 parts by weight of tribasic calcium phosphate and0.01 part by weight of dodecyl-sodium benzenesulfonic acid to 400 partsby weight of distilled water, thereby to dissolve the tribasic calciumphosphate. The polymerizable composition containing the DN-5 was addedto the dispersion medium in which the tribasic calcium phosphate hadbeen dissolved. While the resultant mixture was stirred at 8000 rpm for15 minutes with the TK Homomixer (manufactured by Tokusyukika Kogyo Co.,Ltd.), sodium hydroxide was added to this mixture so that the tribasiccalcium phosphate was separated and the polymerizable compositionabove-mentioned was suspended. The suspension was transferred to aseparable flask and subjected to normal stirring at 80° C. under astream of nitrogen to achieve polymerization for 5 hours.

The resultant particles were taken out. The particles thus taken outwere treated with dilute acid and washed with water. The particles thuswashed were dried, thus producing toner. According to the particle sizedistribution of this toner as measured with a coulter counter, thevolumetric average particle size was 9.5 μm and fine particles having aparticle size of 5 μm or less were contained at a ratio of 0.5% or less.The toner and a ferrite carrier were mixed and then electrostaticallycharged by friction. The toner electrostatic charge as measured by theblow-off method was -44 μc/g. Likewise, as in Example 2, thedistribution of electrostatic charge of this developer was measured withapparatus for measuring the electrostatic charge of toner. Thedistribution of electric charge thus measured was very sharp withoutnon-charged or reversely charged toner particles, as shown in FIG. 4.

Example 8 (production of the second toner)

Toner was prepared by suspension polymerization in the same manner asExample 7 except for the use of 24 parts by weight of the DN-6 (Rf valueof 0.92 to 0.97) instead of the DN-5 used in Example 7, and 46 parts byweight instead of 60 parts by weight of styrene, and the additional useof 30 parts by weight of n-butylmethachlylate. The distribution ofparticle size of this toner was measured with a coulter counter.According to the measurement result, the volumetric average particlesize was 9.8 μm and fine particles having a particle size of 5 μm orless were contained at a ratio of 0.6% or less.

The electrostatic charge of this toner as measured by the blow-offmethod was -40μc/g. The distribution curve of electrostatic charge wasvery sharp without non-charged or reversely charged toner particlesshown.

Example 9 (production of the second toner)

Toner was prepared in the same manner as in Example 7 except that 10parts by weight of the DN-7 (Mw=8.7×10⁵) (Rf value: 0.86 to 0.99) wasused instead of the DN-5 (Mw=2.6×10³) used in Example 7, the DN-7 havinga greater molecular weight than that of the DN-5. The viscosity of thepolymerizable composition became high. Hydrochloric acid was added to adispersion medium as obtained by mixing and adding 7.0 parts by weightof tribasic calcium phosphate and 0.02 part by weight of dodecyl-sodiumbenzenesulfonic acid to 400 parts by weight of distilled water, therebyto dissolve the tribasic calcium phosphate. The polymerizablecomposition containing the DN-7 was added to the dispersion medium inwhich the tribasic calcium phosphate had been dissolved. The resultantmixture was suspended and polymerized at 9000 rpm with the TK Homomixer(manufactured by Tokusyukika Kogyo Co., Ltd.), thereby to produce toner.According to the distribution of toner particle sizes as measured, thevolumetric average particle size was 9.8 μm and fine particles having 5μm or less were contained at a ratio of 0.6% or less. The electrostaticcharge of the toner as measured by the blow-off method, was -40 μc/g.The distribution curve of electrostatic charge was very sharp withoutnon-charged or reversely charged toner particles shown.

Comparative Example 3 (production of the second toner)

Toner was prepared by suspension polymerization in the same manner as inExample 8 except that 10 parts by weight of the DN-4 (Rf value of 0.42to 0.99) was used in Comparative Example 3. After completion of thepolymerization, the suspension was observed with a light microscope, andit was found that the particles having a particle size of about 10 μmprior to polymerization had been reduced in particle size to 8 μm. Theparticles were then treated with dilute acid and washed with water untilemulsion-polymerized particles disappeared. The particles thus washedwere then dried, thus producing toner.

The toner electrostatic charge as measured by the blow-off method was aslow as -10 μc/g. The distribution of electrostatic charge showed a greatnumber of reversely charged or non-charged toner particles, as shown inFIG. 5. The toner yield was equal to 50%.

Example 10 (production of the second toner)

    ______________________________________                                        (Component)            (Quantity)                                             ______________________________________                                        SN-2 (Rf value of 0.7 to 0.99)                                                                       24    parts by weight                                  Styrene                46    parts by weight                                  n-butylmethacrylate    30    parts by weight                                  Graphitized carbon black                                                                             5     parts by weight                                  (MA-100 manufactured by                                                       Mitsubishi Kasei Co., Ltd.)                                                   Polypropylene of low molecular                                                                       1.5   part by weight                                   weight (BISCOL 550P manufactured                                              by Sanyo Kasei Co., Ltd.)                                                     Initiator of polymerization                                                                          4     parts by weight                                  (AIBN)                                                                        ______________________________________                                    

The components above-mentioned were mixed to prepare a polymerizablecomposition.

Hydrochloric acid was added to a dispersion medium as obtained by mixingand adding 5.5 parts by weight of tribasic calcium phosphate and 0.01part by weight of dodecyl-sodium benzenesulfonic acid to 400 parts byweight of distilled water, thereby to dissolve the tribasic calciumphosphate. The polymerizable composition containing the SN-2 was addedto the dispersion medium in which the tribasic calcium phosphate hadbeen dissolved. While the resultant mixture was stirred at 8000 rpm for15 minutes with the TK Homomixer (manufactured by Tokusyukika Kogyo Co.,Ltd.), sodium hydroxide was added to this mixture so that the tribasiccalcium phosphate was separated and the polymerizable compositionabove-mentioned was suspended. The suspension was transferred to aseparable flask and subjected to normal stirring at 80° C. under astream of nitrogen to achieve polymerization for 5 hours. The resultantparticles were taken out. The particles thus taken out were treated withdilute acid and washed with water. The particles thus washed were dried,thus producing toner.

According to the particle size distribution of this toner as measured,the volumetric average particle size was 8.4 μm and fine particleshaving a particle size of 5 μm or less were contained at a ratio of 0.6%or less. The toner electrostatic charge as measured by the blow-offmethod was -32 μc/g. According to the result of measurement, thedistribution curve of electrostatic charge was very sharp withoutnon-charged and reversely charged toner particles shown.

Comparative Example 4 (production of the second toner)

In the same manner as in Example 10, a polymerizable composition wasprepared with the use of the SN-1 (Rf value of 0 to 1.0) instead of theSN-2 used in Example 10. Likewise, as in Example 10, hydrochloric acidwas added to a dispersion medium as obtained by mixing and adding 5.5parts by weight of tribasic calcium phosphate and 0.01 part by weight ofdodecylsodium benzenesulfonic acid to 400 parts by weight of distilledwater, thereby to dissolve the tribasic calcium phosphate. Thepolymerizable composition containing the SN-1 was added to thedispersion medium in which the tribasic calcium phosphate had beendissolved. While the resultant mixture was stirred at 6000 rpm for 15minutes with the TK Homomixer (manufactured by Tokusyukika Kogyo Co.,Ltd.), sodium hydroxide was added to this mixture so that the tribasiccalcium phosphate was separated and the polymerizable compositionabove-mentioned was suspended.

When the suspension was observed with a optical microscope, it was foundthat all particles having a particle size of about 8 μm beforepolymerization had disappeared. Even though treated with dilute acid,washed with water and dried, the particles could not be used as toner.

As apparent from Examples 7 to 10 and Comparative Examples 3 to 4, theDN-5 and the DN-6 were prepared under the same polymerization conditionsexcept for the conditions of flask and charge amount, but presentdifferent Rf values serving as indexes of lipophilic property. The useof the DN-7 of which average molecular weight is higher than that of theDN-5 or DN-6, caused the viscosity of the polymerizable composition tobecome higher. However, by increasing the stirring speed and the amountsof the dispersion stabilizer and the surface active agent, it waspossible to prepare toner presenting a sharp distribution of particlesize and good electrostatic chargeability without emulsion particlesproduced, likewise in Examples 7 and 8 using the DN-5 and DN-6,respectively.

According to Example 10, the toner was prepared with the use of the SN-2(presenting the Rf value in a range from 0.7 to 1.0) which had beenobtained by dispersing and dissolving the composition in the THF and byloading the composition in water to remove the unnecessarycopolymerizable composition. The toner of Example 10 produced very goodresults. On the other hand, no toner was obtained with the use of theSN-1 of Comparative Example 4 (presenting the Rf value of 0 to 0.99)which remained containing the unnecessary copolymerizable composition.

It was understood that any toner as obtained with the use of theelectric charge controlling resin presenting the Rf value in a preferredrange, was good and that the production control using a thin-layerchromatography at the time of production of the electric chargecontrolling resin was very effective in checking the quality of tonerproduced on a full scale.

FIG. 6 shows apparatus for measuring the distribution of tonerelectrostatic charge used for Examples and Comparative Examplesabove-mentioned.

As shown in FIG. 6, this apparatus is provided in a cylindrical housing1 thereof with a separation unit 2 for separating toner from adeveloper, a counting unit 3 for measuring the distribution ofelectrostatic charge of separated toner, and a suction device 11 such asan air pump or the like.

The separation unit 2 and the counting unit 3 are divided from eachother by a partition plate 7. At a position slightly lower than theposition of this partition plate 7, the lateral wall of the housing 1has communication holes 1a for introducing air into the housing 1. Airflow arranging filters 8 are disposed at positions slightly lower thanthe positions of the communication holes 1a.

In the separation unit 2, compressed air is blown to a developer as heldon a magnet 4 by an air needle 5, so that light-weight toner alone isblown up and scattered with a carrier magnetically adsorbed by themagnet 4 remaining thereon.

A funnel 6 as supported by the partition plate 7 is disposed between theseparation unit 2 and the counting unit 3. The funnel 6 has, at theupper end thereof, a receiving port 6d which projects upwardly from thepartition plate 7. The funnel 6 has, at the lower end thereof, atapering portion 6a which passes through the filters 8 and faces thecounting unit 3.

In the counting unit 3, a D.C. source supply B is applied to a pair ofelectrode rods 9a, 9b embedded in the lateral wall of the housing 1,thereby to form horizontal parallel electric fields between theelectrode rods 9a, 9b. A filter 10 is also disposed.

The suction device 11 is adapted to form not only a main flow of airwhich is introduced from the outside of the housing 1 and which flows tothe counting unit 3 through the communication holes 1a and the air flowarranging filters 8, but also a flow of air adapted to suck the tonerinto the funnel 6, the last-mentioned air flow being formed above thefunnel 6.

According to the apparatus having the arrangement above-mentioned, tonerparticles separated by the separation unit 2, collected by the funnel 6and introduced into the counting unit 3, are adapted to fallperpendicularly along the air flows formed by the suction device 11. Thetoner particles then reach the filter 10 through the gap between theelectrode rods 9a, 9b. At this time, each of the toner particles fallswhile receiving, in the horizontal parallel electric fields between theelectrode rods 9a, 9b, vertical gravity V and a horizontal Coulomb'sforce H according to the electrostatic charge. Accordingly, each tonerparticle is dispersed, on the filter 10, to the position correspondingto the mass and electrostatic charge thereof. Based on the distributionof toner particle falling positions, the distribution of tonerelectrostatic charge may be calculated by an image processing. With thisapparatus, there may be obtained the number fraction of electrostaticcharge per toner particle in each of the ranges of particle size (2 to 5μm, 5 to 7 μm, 7 to 10 μm, and 10 to 15 μm.

What is claimed is:
 1. An electric charge controlling resin comprising apolymer obtained by copolymerization between at least one oil-solublemonomer selected from a group consisting of a vinyl aromatic hydrocarbonmonomer, an acrylic monomer, a vinyl ether monomer, a diolefin monomerand a monoolefin monomer, and at least one water-soluble monomer,wherein the water-soluble monomer is a sodium styrene sulfonate, saidpolymer being adjusted such that a flow rate, Rf, is in the range from0.5 to 1.0, as measured by thin layer chromatography wherein a silicagel is used as an absorbent and ethyl acetate is used as a developingsolvent.
 2. A toner including a binding resin and the electric chargecontrolling resin according to claim 1 dispersed in the binding resin.3. An electric charge controlling resin according to claim 1, whereinsaid polymer is obtained by a dispersion polymerization in a mixturemedium of water and a water-miscible organic solvent and in the presenceof a dispersion stabilizer.
 4. An electric charge controlling resinaccording to claim 1, wherein said polymer is dissolved in awater-soluble organic solvent to form a resultant solution, and theresultant solution is loaded into water, such that said flow rate iswithin the range of 0.5 to 1.0.
 5. A toner comprising spheric particles,which particles are obtained by a method comprising the steps ofdispersing said electric charge controlling resin of claim 1 withcoloring agents in a radically polymerizable monomer capable of forminga binding resin, suspending the obtained radically polymerizablecomposition in water, forming oil drop particles having sizes in therange of 5 to 30 μm, and polymerizing the composition in the presence ofan initiator of radical polymerization.
 6. An electric chargecontrolling resin as in claim 1, wherein said flow rate is in the rangeof 0.7 to 1.0.
 7. A method for producing a toner, comprising:dispersingan electric charge controlling resin with a coloring agent in aradically polymerizable monomer capable of forming a binding resin, saidelectric charge controlling resin obtainable by copolymerization betweenat least one oil-soluble monomer selected from a group consisting of avinyl aromatic hydrocarbon monomer, an acrylic monomer, a vinyl ethermonomer, a diolefin monomer and a monoolefin monomer, and at least onewater-soluble monomer, wherein said water-soluble monomer is a sodiumstyrene sulfonate, said polymer being adjusted such that a flow rate,Rf, is in the range from 0.5 to 1.0, as measured by thin layerchromatography, wherein a silica gel is present as an absorbent andethyl acetate is present as a developing solvent; suspending theradically polymerizable monomer in water; forming oil drop particleshaving particle sizes in the range of 5 to 30 μm; and polymerizing theparticles in the presence of an initiator of radical polymerization.